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  1. #11

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    Quote Originally Posted by pstake View Post
    Thanks. this is great.

    It states that 10g should be dissolved in 500ml of water to create a stock solution; and 30ml of stock solution added per liter of developer.
    Benzotriazole is difficult to dissolve in water and its solubility is about 20 g/l. Therefore trying to dissolve 10 g in 500 ml of water may be a bit difficult. Solutions more concentrated than 1% may exhibit precipitation of the solid when stored at lower temperatures. Traditionally photographers have used a 1% solution for this reason.

    The object with any restrainer whether BZT or KBr is to use as little as possible to avoid speed loss and tonal changes. Therefore it is unwise to start with 30 ml/l. One needs to do a bit of testing first.
    Last edited by Gerald C Koch; 08-22-2013 at 10:39 PM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  2. #12
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    Quote Originally Posted by Gerald C Koch View Post
    Benzotriazole is difficult to dissolve in water and its solubility is about 20 g/l. Therefore trying to dissolve 10 g in 500 ml of water may be a bit difficult. Solutions more concentrated than 1% may exhibit precipitation of the solid when stored at lower temperatures. Traditionally photographers have used a 1% solution for this reason.
    Isn't 20g/l and 10g/500ml the same ratio?

  3. #13
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    Quote Originally Posted by Gerald C Koch View Post
    For a 1% solution dissolve 10 g in 1 liter of water. Since you must use hot water to avoid doing a lot of stirring the volume will contract when it cools and you need to add a little additional to bring it up to 1 liter. Sorry if my post didn't make this completely clear.

    BTW I found the PDF article very interesting and worthy of being posted on its own thread for access to a larger body of readers.
    Oh, okay — this makes sense. Thank you.

    By the way, I tested the Brovira tonight and there was no noticeable fog after 3.5 minutes in the dev, then stop and 2 minutes in the fix. It has a creamier base than I'm used to, and a different finish (that I like) ... "crystal."

  4. #14

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    I dissolve my Benzo in Alcohol (the cheap 50% isopropyl works fine). It dissolves in seconds as opposed to water (Biiig pita!).

  5. #15
    K-G
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    Try without benzotriazole first. Last year I printed on my last remaining stack of Brovira. It did not show any fogging.

    Karl-Gustaf
    Karl-Gustaf Hellqvist

    www.heliochroma.com

  6. #16
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    Quote Originally Posted by K-G View Post
    Try without benzotriazole first. Last year I printed on my last remaining stack of Brovira. It did not show any fogging.

    Karl-Gustaf
    Thanks, KG. Mine didn't show any fog either when I tried a cut piece last night.

  7. #17

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    What's the function of BZT in developers? We use this chemical in my industry as a corrosion inhibitor.

  8. #18
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    Quote Originally Posted by RattyMouse View Post
    What's the function of BZT in developers? We use this chemical in my industry as a corrosion inhibitor.
    It slows down activity. This aids in reducing fog in old film and paper, and leads to a cooler tone in prints.
    Matt

    “Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

    Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

  9. #19

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    Benzotriazole is what is known as a restrainer. In its action it is similar to potassium bromide. It suppresses development of active centers which would result in fog. When used in excessive amounts active centers associated with an image are also suppressed resulting in a general loss of film speed.

    Organic restrainers are often called anti-foggants while inorganic ones like potassium bromide are just called restrainers. Developing agents differ in their ability to distinguish between image centers and fog centers. A developing agent like sodium dithionite has little ability to distinguish between these two centers. This is in contrast to the developing agents which are most often used like Metol. Therefore a restrainer may be required for a particular developer while not for another.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  10. #20
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    Thank you Gerald,
    I needed this.

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